Synorogenic gold mineralization in granite-greenstone terranes: the deep connection between extension, major faults, synorogenic clastic basins, magmatism, thrust inversion, and long-term preservation
Bibliographic record
Abstract
Structurally controlled "lode gold" systems within or in proximity to major fault zones (colloquially known as "breaks") represent a dominant deposit type in Canada, particularly in Archean cratons of the Canadian Shield. This paper describes some of the critical characteristics of these deposits, specifically their relationship to the major faults and the complicated kinematic history of these faults, and to the panels of synorogenic clastic (±volcanic) rocks that occur along these faults. The synthesis that emerges is mainly based on the Timmins area, Canada's most prolific gold camp, but critical elements apply equally to and have been ground-truthed in other gold camps, i.e., Kirkland Lake, the Abitibi more generally, the Rice Lake belt, Yellowknife, and the Agnew camp of the Yilgarn craton. In all of these areas, the key faults cut early foldand- thrust structures and were likely initiated as crustal-scale, synorogenic extensional faults in association with a flare-up in synorogenic, typically more alkaline magmatism. Extension, the associated mantlederived magmatism, and the resulting thermal pulse into the lower crust were likely the ultimate drivers of the gold mineralizing events. Synorogenic extension also minimized post-orogenic uplift, thus playing an important indirect role in preservation of the upper crustal depositional environments. Following synorogenic extension and the initiation of the magmatic and hydrothermal processes that produced the gold systems, the crustal-scale faults were invariably inverted as thick-skinned thrusts, burying synorogenic basin remnants and gold deposits in their structural footwall, while deposits were removed or largely eroded from the structural hanging wall of these thrusts. This thrust inversion thus plays a critical role in the preservation of the gold endowment and explains the fundamental asymmetry across most of these camps. Gold mineralization appears to have peaked during the thrust-inversion stage and subsequent shortening, but had waned prior to final strike-slip overprinting of the fault zones. The integrated model provides a coherent guide for identifying and analyzing similar settings in more remote settings of northern Canada.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".